Technical Field
The present invention relates to a substrate processing method and a substrate processing apparatus.
Description of Related Art
As one of the manufacturing steps of a semiconductor device such as IC, a substrate processing step using an ALD (Atomic Layer Deposition) method and a CVD (Chemical Vapor Deposition) method is performed. A vertical substrate processing apparatus is used as a substrate processing apparatus for performing the substrate processing step. The vertical substrate processing apparatus includes a reaction tube for forming a processing chamber; a gas supply unit for supplying processing gas into the processing chamber; an exhaust unit for exhausting inside of the processing chamber; and a heater unit for heating the inside of the processing chamber. The vertical substrate processing apparatus is capable of processing a plurality of substrates by a single batch processing, and therefore has a characteristic that throughput (productivity) is higher than a sheet-type substrate processing apparatus.
FIG. 20 is a schematic view showing a structure of a processing furnace of a conventional vertical substrate processing apparatus. This processing furnace includes a reaction tube 203′ made of, for example, quartz (SiO2). A processing chamber 201′ is formed in the reaction tube 203′. Boats (not shown) as substrate holding tools for supporting a plurality of wafers as substrates, are loaded into the processing chamber 201′ in multiple stages. The processing furnace includes a gas supply unit for supplying processing gas such as source gas and oxide gas into the processing chamber 201′. The gas supply unit includes a first gas supply tube 232a′ for supplying the source gas (such as a gas containing element Zr); a second gas supply tube 232b′ for supplying the oxide gas (such as an ozone (O3) gas); a first gas supply nozzle 233a′ connected to the first gas supply tube 232a′; and a second gas supply nozzle 233b′ connected to the second gas supply tube 232b′. The first gas supply nozzle 233a′ and the second gas supply nozzle 233b′ are respectively provided in the reaction tube 203′, so as to be vertically extended from a lower part of the reaction tube 203′ to a ceiling part of the reaction tube 203′ along an inner wall of the reaction tube 203′. A plurality of gas jet holes are respectively provided in the first gas supply nozzle 233a′ and the second gas supply nozzle 233b′. An arrangement pitch of the gas jet holes is made to be same as a support pitch of the plurality of wafers (not shown) supported by the aforementioned boats (not shown) in multiple stages. The gas jet holes are constituted so that the processing gas can be flown along an upper surface of each wafer. The first gas supply tube 232a′ is connected to a source gas supply source for supplying source gas, through a valve 243a′. The second gas supply tube 232b′ is connected to an oxide gas supply source for supplying oxide gas through a valve AV2′. Note that although not shown, the processing furnace further includes a carrier gas line for supplying N2 gas, being a carrier gas (purge gas), into the processing chamber 201′, and an exhaust unit for exhausting an atmosphere in the processing chamber 201′.
For example, in the substrate processing step using the ALD method, first source gas supplying step→N2 purging step→first exhausting step→second source supplying step→N2 purging step→second exhausting step are set as one cycle, and this cycle is repeated multiple number of times. In the first source gas supplying step, the valve AV2′ is closed and the valve 243a′ is opened, while exhausting the inside of the processing chamber 201′ by the exhaust unit (not shown), and the source gas is supplied into the processing chamber 201′. Thus, the source gas jetted from each gas jet hole of the first gas supply nozzle 233a′ is flown horizontally on each wafer, then is adsorbed on the surface of the wafer, to thereby form a base film on the wafer. In the N2 purging step, the valve AV2′ and the valve 243a′ are closed while continuing exhaust of the inside of the processing chamber 201′ by the exhaust unit (not shown), and N2 gas, being purge gas, is supplied into the processing chamber 201′ from a carrier gas line (not shown). Thus, the source gas remained in the processing chamber 201′ is discharged from the processing chamber 201′, and the inside of the processing chamber 201′ is purged. In the first exhausting step, supply of the N2 gas from the carrier gas line (not shown) is stopped, with the valve AV2′ and the valve 243a′ closed, while continuing the exhaust of the inside of the processing chamber 201′ by the exhaust unit (not shown). Thus, the inside of the processing chamber 201′ is exhausted and cleaned. In the oxide gas supplying step, O3 gas, being the oxide gas, is supplied into the processing chamber 201′, with the valve 243a′ closed and the valve AV2′ opened, while continuing the exhaust of the inside of the processing chamber 201′. Thus, the oxide gas jetted from each gas jet hole of the second gas supply nozzle 233b′ is flown horizontally on each wafer, which is then reacted with the base film formed on the wafer, to thereby form an oxide film on the wafer.
Thus, in the ALD method and the CVD method, oxide gas containing, for example, ozone, being oxide species, is used as a second source, so that ozone is horizontally supplied along an upper surface of each wafer. However, if processing is performed by a conventional vertical substrate processing apparatus, there is a tendency that oxidation is easily advanced on an outer peripheral side of the wafer to which ozone is supplied easily, and oxidation is delayed on a center side of the wafer to which ozone is hardly supplied. Therefore, a film thickness distribution and composition distribution in a surface of the wafer are deteriorated, thus generating variation in the characteristic of the semiconductor device, and a manufacturing yield of the semiconductor device is deteriorated in some cases.
Therefore, the following two methods have been examined. One of them is a method of preventing a delay in oxidation in the center part of the wafer, by increasing a flow speed of the oxide gas containing ozone on the wafer. The other one is a method of processing substrates uniformly in the surface, by eliminating an uneven oxidation over the whole wafer, by supplying to the wafer, a large flow rate of the oxide gas containing high density ozone.
However, in the former method, sufficient improvement is not observed, and it is difficult to sufficiently prevent the delay in oxidation in the center part of the wafer, and it is difficult to improve the manufacturing yield of the semiconductor device.
Further, in the latter method, the yield can be improved. However, a flow rate of high density ozone that can be supplied at once is reduced, in terms of a performance of ozonizer (not shown) of the oxide gas supply source, then supply time of ozone is prolonged, and throughput (productivity) is deteriorated.
An object of the present invention is to shorten a processing time and improve uniformity of a film thickness in the surface, when the oxide film is formed by supplying the oxide gas onto the substrate.